The design of a vehicle has typically been governed, at least in part, by both cosmetic and utilitarian considerations. Cosmetic-based design features are intended to enhance the visual appeal of a vehicle to the consuming public. Utilitarian-based features, on the other hand, are designed to achieve the intended purpose of the vehicle. For example, the engine and vehicle size are determined, in part, by how many passengers the vehicle will carry, or what size load will be transported. In recent years, cosmetic and utilitarian concerns have merged to increase focus on preserving cosmetic appeal, while also making the vehicles more efficient so as to reduce fuel costs.
The amount of power needed to move a vehicle increases as a function of the vehicle speed because of aerodynamic drag. The amount of power necessary to overcome that increased drag directly translates to increased fuel consumption, and thus increased cost of operation. In the United States trucking industry, an estimated 1.7 million trucks use 23 billion gallons of diesel fuel every year, and 65-70% of the energy expended in fuel is to overcome aerodynamic drag on the truck and trailer. Many aerodynamic improvements have been made to the front sides of trucks and trailers to minimize costly aerodynamic drag. These improvements have helped the average fuel economy in the trucking industry rise from 4.5 miles per gallon in the 1980's to approximately 6 miles per gallon today.
While those aerodynamic design improvements at the front of a truck and trailer have resulted in some improvement to fuel economy, aerodynamic drag remains a costly problem. This problem is exacerbated by the typical design of the back end of most trailers, which is vertically squared-off. This squared-off rear end creates significant drag on the vehicle, which consumes large amounts of fuel. As with any vehicle, when the trailer body moves through the air, a mass of air is displaced and must flow around the trailer. As the air flows toward the squared-off back end of a trailer, an area of low pressure is created. This area causes a sudden, high-energy, chaotic inrush of turbulent air which creates drag on the rear of the trailer.
Aerodynamic drag reduction systems in the prior art have not been widely accepted or commercially successful in the trucking industry. The most significant drawbacks in almost all known systems are the following: (1) the complicated processes for installing the systems on a vehicle, (2) the need to permanently modify the vehicle to install the system, (3) the functional difficulties added by the installation and operation of the device such as unloading and loading for trucks with trailers, and (4) the time-consuming nature of deploying and stowing the systems at each loading or unloading station.
While many solutions to improve the aerodynamic drag at the rear of the truck and trailer have been suggested, none have been widely adopted in the United States by trailer manufacturers or trucking companies. Various reasons have caused this dilemma. First, trailer manufacturers generally design a trailer to maximize its interior cargo space given fixed external dimensions mandated by federal highway regulations. Consequently, aerodynamic design is not the manufacturer's primary design concern. Second, trailers are often loaded and unloaded at loading docks which require the driver to back the trailer up flush against the loading dock. Any aerodynamic device, therefore, must be easily removable or repositionable to ensure flush loading with the dock.
There is clearly room for improvement in aerodynamic devices for trailers to overcome the above-mentioned issues. For instance, it would be desirable to create an aerodynamic device that significantly reduces the aerodynamic drag on a trailer caused by the squared-off back end of the trailer. Such a device should also be quick and easy to collapse or deploy during load transfers. It would also be desirable to create such a device inexpensively in order to entice the trucking industry to adopt widespread use of this device.